Focus TDCi 1.8 fuel economy with Bio Diesel?

Hi there-I have had a 3 door Focus on a 54 plate for about 18 months
now -the fuel economy I always thought was quite poor,but since using
Bio diesel it has gone even more downhill .
If anyone can give me a clue about this I would be very grateful
Filling up usually costs me about 40-45 quid-using normal diesel, this
would usually give me about 300-350 miles depending if I was doing more
motorway/dual carriageway driving.
With the Bio diesel I am getting maybe 250 miles- I have no idea why
the mileage is so low, my only guess is that the A/C is on constantly
,even though I never switch it on.
As it is under warranty still I have taken it the dealer a few times as
the throttle sometimes sticks in 1st,each time they fix it ,and a few
weeks later it goes wrong again.
If I drove like a maniac every day I could understand but I am
Family Man these days!I must be as its Saturday night.
TIA

Bob Minchin wrote:
> "Paul Johnson" <validatpart.DeleteThis@yahoo.co.uk> wrote in message
> news:1168121865.078944.323870@s34g2000cwa.googlegroups.com...
> > Hi there-I have had a 3 door Focus on a 54 plate for about 18 months
> > now -the fuel economy I always thought was quite poor,but since using
> > Bio diesel it has gone even more downhill .
> > If anyone can give me a clue about this I would be very grateful
> > Filling up usually costs me about 40-45 quid-using normal diesel, this
> > would usually give me about 300-350 miles depending if I was doing more
> > motorway/dual carriageway driving.
> > With the Bio diesel I am getting maybe 250 miles- I have no idea why
> > the mileage is so low, my only guess is that the A/C is on constantly
> > ,even though I never switch it on.
> > As it is under warranty still I have taken it the dealer a few times as
> > the throttle sometimes sticks in 1st,each time they fix it ,and a few
> > weeks later it goes wrong again.
> > If I drove like a maniac every day I could understand but I am
> > Family Man these days!I must be as its Saturday night.
> > TIA
> >
> Documentation for my 54 plate 2.0TDCi warns that more that 5% bio diesel
> invalidates the warranty. This stuff might be alright for older 'tractor'
> diesel engines but it is not good for the fine bore injectors used in recent
> engines.
> Also my expeiments with fuel efficiency and aircon show no discernable
> difference in diesel useage with or without aircon.
>
> Bob\


Thanks for that-can you give me an average mileage you get per fill up
please? Just so I have an idea where I stand,before taking it back to
the dealer.
TIA